The present invention relates to quartz crystal vibrators and more particularly, to quartz crystal tuning fork vibrators.
Quartz crystal tuning fork vibrators are in widespread use today in various applications and because of their relatively low resonance frequency and stability of performance, such vibrators are particularly suitable for use in watches and other timepieces. The techniques currently used to manufacture the quartz crystal tuning fork vibrators are similar to those used to manufacture electronic integrated circuits and in general, such techniques comprise a combination of mechanical working steps and etching steps.
One drawback of these techniques is that the resultant tuning fork vibrator requires a large amount of frequency adjustment before it can be embodied in a timepiece. It is very difficult to mass-produce quartz crystal tuning fork vibrators having the desired resonance frequency by means of the conventional mechanical working steps and therefore it is standard practice to individually adjust the resonance frequency of each vibrator by selectively cutting off end portions of the tuning fork tines in order to achieve the desired resonance frequency. This additional cutting off step is both time consuming and costly and reduces the production efficiency.
After formation of the quartz crystal tuning fork vibrator, it is necessary to attach electrodes to the tuning fork arms or tines to enable excitation of the vibrator. To this end, the technique used to form electrodes by photo-etching operations used in integrated circuit technology has been adopted to form electrodes on the turning fork vibrator. The formation of electrodes in this manner is desirable in that many sets of electrodes can be applied to many quartz crystal tuning fork vibrators during one operation thereby greatly reducing the manufacturing costs. However, in order to form the electrodes by photo-etching operations, it is necessary that the sheet of quartz crystal material forming the tuning fork vibrators by very thin, generally on the order of 50.mu.-100.mu.. Tuning fork vibrators of this thickness, which is considerably less than the thickness of vibrators currently in use, then to undergo vibration at larger amplitudes than vibrators which are thicker and this is disadvantageous in that the long-term reliability and life of a tuning fork vibrator is largely affected by the magnitude or amplitude of the end point vibration of the tuning fork tines. The present invention resolves this problem by providing a quartz crystal tuning fork vibrator which operates at its resonance frequency with a lower amplitude of end point vibration of the tuning fork tines thereby extending the life and long-term reliability of the vibrator.